Circuit arrangement for gaseous discharge tubes



Dec. 21, 1943.

o. M. DUINKER CIRCUIT ARRANGEMENT FOR GASEOUS DISCHARGE TUBES Filed May 1. 1940 :5 comma/ ff/14M Patented Dec. 21, 1943 CIRCUIT ARRANGEMENT FOR GASEOUS DISCHARGE TUBES Daniel Marie Duinker, Eindhoven, Netherlands, assignor, by mesne assignments, to Hartford National Bank and Trust Company, Hartford,

Conn, as trustee Application May 1, 1940, Serial No. 332,834 In Germany April 17, 1939 1 Claim.

reliable ignition is not always ensured when there is a reactive load, for instance a welding transformer, in the anode circuit of the tube. This difficulty is due to the fact that the reactance of such a load may be so high that the cathode current cannot rise sufiiciently quickly to reach such a Value within the duration of the ignition voltage impulse that a safe establishing of the arc is guaranteed.

In accordance with the invention, I overcome the above difiiculty and obtain reliable ignition by connecting in parallel with the reactive load, an ohmic resistance which has such a value that with the anode current used the cathode current attains within the uration of an ignition-voltage impulse a value which is sufficiently high for safe ignition. It will be understood that on the other hand to avoid unnecessary energy loss the resis ance should not be chosen lower than is necessary for producing the desired effect.

The ignition-voltage impulses used in practice generally have a duration of the order of ma nitude of 10- seconds or less, and I have found that, when usin a mercury'cathode, a cathode current of at least 1 ampere will generally be sufficient to ensure safe ignition within this period. Since the load current, e. g. in welding apparatus, is generally of the order of magnitude of several hundreds to thousands of amperes, it will be understood that the energy loss caused by the cathode current of the order of magnitude of 1 amp. is negligible.

In order that the invention may be clearly understood and readily carried into effect I shall describe the same in more detail with reference,

to the appended drawing in which the single figure is a schematic diagram of a circuit arrangement embodying the invention.

As shown in the drawing, a mercury-cathode gaseous-discharge tube I has an anode 2 connected through the primary winding 3 of a welding transformer 4 to one end of an alternating current supply whose other end is connected through a conductor 5 to the mercury cathode 6 of tube l.

The tube I has a control electrode I to which ignition-voltage impulses of short duration are applied during operation of the tube. For this purpose a synchronous motor 8 energized by the alternating current supply drives a commutator 9 of insulating material having a conductive portion l0 adapted to connect two brushes II and [2. brush I2 is connected through a battery l3 to the conductor 5.

In accordance with the invention I connect in parallel with the load 3, an ohmic resistance M which is of such value that the cathode current of tube I will reach a value sufficient to achieve reliable ignition during the intervals in which each of the voltage impulses is applied to the control electrode 1. In the circuit illustrated this current should be at least 1 amp. Let it be assumed that the ignition, as is usual with inductive loads, takes place at about the top of the voltage wave and let it be assumed that the R. M. S. value of the A. C. supply is 500 volts, the anode voltage at the moment of ignition will be about 500 V2, i. e. about 700 volts. In order to produce immediately the said cathode current of at least 1 amp. the resistance M has to have a value of about 700 ohms or less in this case.

The gaseous discharge tubes used in circuit arrangements according to the invention may have ignition control electrodes in the form of a capacitative electrode, for example a starting band, or an electrode which is provided with a glass coating or is built up of semi-conductive materials and is continuously immersed in a liquid cathode, for instance a mercury cathode.

Although I have described my invention with reference to specific examples and applications, I do not desire to be limited thereto because obvious modifications will appear to one skilled in thi art.

What I claim is:

A circuit arrangement comprising a gaseous arc-discharge tube having an anode, a mercury cathode, and an ignition electrode, an anode circuit for said tube including a reactive load, means for applying ignition voltage impulses of the order of magnitude of 10' sec. or less to said ignition electrode, and means to bring the cathode current to a value of at least 1 amp. within the duration of each impulse, said latter means including an ohmic resistance connected across said load.

DANIEL MARIE DUINKER.

Brush H is connected to electrode 1 and 

